Harvard Health Letter

Ask the doctor: Seborrheic keratoses

Q. I have a bad case of seborrheic keratoses on my back and chest. What can you tell me about this skin problem?

A. These growths on the skin can be unsightly and get irritated and bleed, but seborrheic keratoses (pronounced seb-o-REE-ik ker-ah-TOE-sees) are very common and noncancerous. Typically, they start as small yellow or tan bumps and then gradually turn dark brown or black and develop a wartlike surface. They appear most often on the face, shoulders, chest, and back. Seborrheic keratoses are usually a little bit raised, so they look like they've been stuck on the surface of the skin. Some Africans, African Americans, and other dark-skinned individuals get a variant of the condition called dermatosis papulosa nigra, which consists of many black lesions on the cheeks.

People sometimes mistake seborrheic keratosis for melanoma, the most serious type of skin cancer, because in both, the growths are dark and have an irregular shape. Smaller, heavily pigmented seborrheic keratoses can, in fact, look a little like melanoma lesions. A dermatologist can usually tell the difference just by looking at them. If there's any doubt, he or she should get a biopsy (a tiny sample from the lesion) for microscopic examination.

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